Method including downhole flow control in solution mining

ABSTRACT

A method for controlling downhole fluid flow in multi-lateral solution mining may include forming a solution mining production well with a plurality of horizontal laterals drilled from a surface to connect and intersect with a horizontal or vertical injection well; and installing a downhole flow control device at the intersection of the horizontal injection well and each of the horizontal laterals. The downhole flow control device may be capable of being adjusted to distribute injection flow as desired through the horizontal laterals. The downhole flow control device may be a sliding sleeve capable of ranging from fully open to full closed to control flow from the injection well into multiple locations within the mineralized zone.

BACKGROUND

The embodiments described herein relate generally to solution mining and, more particularly, to a method utilizing downhole flow control via a sliding sleeve or other downhole flow control devices for solution mining. Specifically, the method includes solution mining of a soluble mineral at depth using a technique that allows for the control of the solvent flow through multiple locations within a solution mining injection well.

Solution mining is a mining method in which the mining of desired minerals is achieved by the injection of a water, or a lean water solution, underground and into a geological formation that contains a desired soluble mineral in a grade concentration that has been determined to be economically feasible for solution mining. The mineral is dissolved into the water, and the rich water solution flows by pump pressure back to the surface and into a mineral recovery processing plant. A solution mining project can be, and has been, an alternative to conventional underground mining projects in which miners and mining equipment work underground to extract and bring to the surface ore in a solid form.

Many solution mining designs utilize casing perforations to direct the location of where the solvent will be injected into the mineralized zone to facilitate the solution mining. Additional perforations are added as required using electric wireline operations and casing perforation tools.

With the continued development of oil and gas horizontal well drilling techniques, horizontal boreholes are being utilized to facilitate solution mining. Some horizontal solution mining designs utilize intersecting horizontal wellbores or multiple intersecting wellbores. However, in the case of multiple intersecting wellbores, the operator does not have the flexibility to adjust the solvent flow through each intersecting borehole.

Therefore, what is needed is a method for controlling the downhole flow of solvent injection for recovery of solution mined minerals, even in multiple intersecting wellbores.

SUMMARY

Some embodiments of the present disclosure include a method for controlling downhole fluid flow in multi-lateral solution mining may include forming a solution mining production well with a plurality of horizontal laterals drilled from a surface to connect and intersect with a horizontal or vertical injection well; and installing a downhole flow control device at the intersection of the horizontal or vertical injection well and each of the horizontal laterals. The downhole flow control device may be capable of being adjusted to distribute injection flow as desired through the horizontal laterals. The downhole flow control device may be a sliding sleeve capable of ranging from fully opened, partially opened at varying degrees, to fully closed to control flow from the injection well into multiple locations within the mineralized zone.

BRIEF DESCRIPTION OF THE FIGURES

The detailed description of some embodiments of the invention is made below with reference to the accompanying figures, wherein like numerals represent corresponding parts of the figures.

FIG. 1 is a plan drawing of one embodiment of the present disclosure, showing a multi-lateral solution mining well system design.

FIG. 2 is a three-dimensional view of one embodiment of the present disclosure, showing a multi-lateral solution mining well system design.

FIG. 3 is a plan drawing of one embodiment of the present disclosure, showing a multi-lateral solution mining well system layout designed to fit within a rectangular land section.

FIG. 4. is a perspective view of an exemplary component used in an embodiment of the present disclosure.

DETAILED DESCRIPTION

In the following detailed description of the invention, numerous details, examples, and embodiments of the invention are described. However, it will be clear and apparent to one skilled in the art that the invention is not limited to the embodiments set forth and that the invention can be adapted for any of several applications.

The method of the present disclosure may be used to facilitate and improve the recovery of solution mined minerals by allowing downhole flow control of injected solvents and may comprise the following elements. This list of possible constituent elements is intended to be exemplary only, and it is not intended that this list be used to limit the device of the present application to just these elements. Persons having ordinary skill in the art relevant to the present disclosure may understand there to be equivalent elements that may be substituted within the present disclosure without changing the essential function or operation of the device.

The various elements of the present disclosure may be related in the following exemplary fashion. It is not intended to limit the scope or nature of the relationships between the various elements and the following examples are presented as illustrative examples only.

As used herein, the following terms and nomenclature have the following definitions:

Solution mine: the wellfield pumping, equipment, and underground caverns as required for solution mining.

Injection well: a well drilled from the surface to the mineralized geological formation at depth to facilitate the injection of a solution, water, or solvent to dissolve a desired mineral into solution.

Injection solution, injection water, or solvent: the water or water solution leaving the process plant and pumped to the wellfield injection wells to facilitate the solution mining.

Downhole flow control device: a device installed within the injection well that can be adjusted as desired to vary the flow through the device into the mineralized geological formation to facilitate the solution mining.

Production well: a well drilled from the surface to the mineralized geological formation to facilitate the flow of the dissolved mineral solution to the surface and subsequently to the processing plant.

Horizontal lateral borehole or lateral: a horizontal borehole drilled along the mineralized geological formation which creates a flow path between the injection well and the production well. Some designs utilize multiple laterals to enhance the distribution of the solvent and to increase the quantity of mineral dissolved into solution.

Production solution or production brine: the water solution containing dissolved materials leaving the wellfield production wells and returning to the process plant for mineral recovery.

Oil and gas horizontal drilling technology: well drilling technology developed by oil and gas drilling companies to steer a wellbore from vertical to horizontal and to direct the wellbore horizontally along a specific geological zone.

Sliding sleeve flow control tool: oil and gas well completion component, such as that shown in FIG. 4 that allows perforations in a steel wellbore liner to be covered or uncovered as desired to control the flow of fluid through the perforations in the liner into a geological formation. Sliding sleeve components have been developed by multiple companies to facilitate hydraulic fracturing in wellbores and more importantly to facilitate hydraulic fracturing in a horizontal wellbore.

Magnetic ranging tool: a specialized oil and gas well drilling technique in which a magnetic source is placed as a target within the targeted wellbore and a magnetic sensor is placed near the drill bit in the drill string within the second wellbore. Using the magnetic source as a beacon, the well is directionally drilled toward the highest magnetic reading. This technique allows two independent boreholes to be drilled in a manner that they intersect at the magnetic source.

By way of example, and referring to FIGS. 1-4, some embodiments of the invention include a method utilizing the use of downhole fluid flow control technology in solution mining. More specifically, the present disclosure comprises use of downhole fluid flow control technology in a multi-lateral solution mining design. For example, the method may comprise using sliding sleeve technology in solution mining, wherein the sliding sleeve is capable of being fully opened, partially opened at varying degrees, and fully closed. The method may further comprise drilling an initial injection borehole utilizing oil and gas horizontal well bore drilling technology, drilling individual boreholes for each cavern in the solution mining wellfield, drilling a recovery borehole using horizontal drilling technology that intersects with each cavern, and directing the sliding sleeve or other downhole fluid control device down the injection borehole to each cavern entrance to control the flow once solution mining begins. Thus, the method of the present disclosure may comprise controlling downhole solution mining injection well flow into multiple locations within a mineralized geological formation, wherein the minerals may comprise potash (KCl), halite (NaCl), trona (Na₂CO₃.NaHCO₃), washing soda (Na₂CO₃.10H₂O); nahcolite (NaHCO₃); glauber salt (NaSO₄.10H₂O), and/or water soluble borate minerals.

As shown in FIG. 1, a typical multi-lateral design 10 comprises a solution mining production well 18 with a plurality, such as seven, horizontal laterals drilled from the surface to connect and intersect with a single horizontal injection well 22. FIG. 1 also illustrates how additional wells 12, 14, 16, and 18 can be arranged to complement well 18 and 22. An exemplary hard boundary 24 is also included within FIG. 1 to illustrate potential mineral rights boundaries that may be encountered. FIG. 2 shows the design 10 in three-dimensions, wherein the horizontal injection well 22 intersects each of the horizontal laterals of the solution mining production well 18. FIG. 2 also illustrates how multiple wells 12, 14, 16 and 20 can be drilled and completed adjacent to wells 18 and 22 to facilitate mineral resource solution mining recovery. As shown in FIG. 3, the multi-lateral design 10 may be arranged to conform to a rectangular land section, wherein the design includes an injection point 32 from the horizontal injection well to each of the horizontal laterals. FIG. 3. also shows the horizontal production well borehole 26 a, the main horizontal well borehole 26 b, the lateral horizontal well boreholes 26 c, the individual solution mining cavern fingers 28, and the envisioned pillars that remain between each of the fingers 30. In particular embodiments, the present disclosure comprises a method for controlling the downhole flow of solvent injection for recovery of solution mined minerals through each of the plurality of horizontal laterals by installing a downhole flow control device at the intersection of the horizontal injection well and each of the horizontal laterals, wherein the flow control devices may be adjusted as necessary to distribute the injection flow as desired through the horizontal laterals.

When a downhole flow control device is not in place, the horizontal laterals with the lowest pressure drops will accept injection flow through the lateral at higher rates than the other laterals, causing the laterals with a higher flow rate to grow larger than the other laterals, thus further reducing the pressure drop for the other laterals. Over time, one (or possibly several) lateral(s) will develop as the predominate flow path through the solution mining cavern. As this occurs, the injection flow through the other laterals is reduced and the overall soluble mineral recovery of the solution mining system will be significantly reduced. On the other hand, when the method of the present disclosure is practiced and a downhole flow control device is in place, the flow through each lateral can be adjusted as necessary to distribute the injection flow through each individual lateral as desired by the solution mining operator.

The downhole flow control device used in the method of the present disclosure may comprise any suitable device for controlling the flow. For example, as shown in FIG. 4 and as discussed above, the downhole flow control may comprise a standard oil and gas downhole sliding sleeve tool 40 that is utilized to control fluid flow while performing hydraulic fracturing of hydrocarbon bearing geological formations. As shown in FIG. 4, the sliding sleeve tool 40 may comprise a sliding sleeve body 42, an upper threaded connection sub 44 operatively attached to the sliding sleeve body 42, a lower threaded connection sub 46 extending from an end of the sliding sleeve body 42, and a sliding sleeve 48 slidably mounted within the sliding sleeve body 42. The sliding sleeve body 42 may include a plurality of sliding sleeve body perforations 50 that may be completely covered, partially covered, or uncovered, depending on the positioning of the sliding sleeve 48. Thus, the oil and gas sliding sleeve tool 40 may be capable of being fully opened, partially opened at varying degrees, and fully closed. The sliding sleeve tool can be actuated to the position desired by the operator using a downhole wireline tractor tool, coiled tubing, or jointed tubing.

The method of the present disclosure may comprise first drilling a horizontal injection well 22 and installing a steel liner with a flow control device(s) and then drilling a multi-lateral production well 18. The flow control device may be installed within the horizontal borehole steel liner of the injection well with a spacing as desired by the solution mining well operator. A magnetic ranging tool, which serves as a directional beacon to guide the horizontal drilling of the intersecting wellbore, may be temporarily installed in the injection well 22 as a target to facilitate the intersection of the horizontal injection well 22 and each of the production well laterals. Advantageously, whenever possible, the intersecting lateral may be drilled about 1 to about 3 meters below the horizontal injection well 22 position, and the final intersection may be achieved by solution mining from the lateral up to the horizontal injection well tool position. As a result, a 1 to 3 meter deep sump may be formed at each injection location, wherein the sumps may allow any insoluble material in the ore zone immediately above the injection point to settle within the sump, reducing the insoluble materials' impact on the downhole low control devices.

As the solution mining cavern is placed into service, a baseline wireline temperature log of the horizontal injection well 22 may be performed. During operation of the solution mining cavern, periodic temperature logs of the horizontal injection well 22 may be performed. If the flow distribution is adequate, the temperature distribution through the injection laterals should be similar to the baseline line temperature log. If the temperature log indicates an anomalous temperature profile, then a downhole injection flow measurement may be performed, wherein the flow measurement may comprise a wireline or coiled tubing E-line flow meter tool that measures the injection flow at the tool's location. As the tool passes each downhole flow control device, the flow may be reduced by the amount of flowing going through the lateral that was passed. At the completion of the flow survey, the flow rate through each lateral may be determined. Using the results of the flow survey, the downhole flow control devices may be adjusted, as necessary, to distribute the injection flow across the laterals, as desired.

If desired or necessary, the method of the present disclosure may further comprise directing injection flow through on to multiple laterals as desired. For example, the operator may wish to focus the injection flow down a single lateral to enhance cavern development or cavern maintenance. In another example, at the end of the solution mining cavern life, the operator may wish to direct the injection flow through the outside laterals to increase the quantity of the desired mineral dissolved into solution.

The above-described embodiments of the invention are presented for purposes of illustration and not of limitation. While these embodiments of the invention have been described with reference to numerous specific details, one of ordinary skill in the art will recognize that the invention can be embodied in other specific forms without departing from the spirit of the invention. Thus, one of ordinary skill in the art would understand that the invention is not to be limited by the foregoing illustrative details, but rather is to be defined by the appended claims. 

What is claimed is:
 1. A method for controlling downhole fluid flow in multi-lateral solution mining, the method comprising: drilling a horizontal injection well; and placing a downhole fluid control device down the horizontal injection well to each cavern entrance in a multi-lateral solution mining design.
 2. A method for controlling downhole fluid flow in multi-lateral solution mining, the method comprising: forming a solution mining production well with a plurality of horizontal laterals drilled from a surface to connect and intersect with an injection well selected from the group consisting of a horizontal injection well and a vertical injection well; and installing a downhole flow control device at the intersection of the injection well and each of the horizontal laterals, wherein the downhole flow control device is capable of being adjusted to distribute injection flow as desired through the horizontal laterals.
 3. The method of claim 2, further comprising using a magnetic ranging tool to facilitate intersection of the horizontal injection well and each of the horizontal, wherein: the ranging tool is positioned within a liner of the horizontal injection well; and each of the horizontal laterals are drilled to intersect the positioning of the magnetic ranging tool, forming intersecting laterals.
 4. The method of claim 3, wherein: each intersecting lateral is drilled about 1 to about 3 meters below the horizontal injection well; and a 1 to 3 meter deep sump is formed at each injection location.
 5. The method of claim 2, further comprising: performing a baseline wireline temperature log of the injection well as the solution mining cavern is placed into service to determine a baseline multi-lateral flow distribution; performing periodic temperature logs of the injection well during operation of the solution mining cavern to determine an anomalous multi-lateral flow distribution; and manipulating the downhole flow control device to enhance injection flow distribution through the horizontal laterals.
 6. The method of claim 2, wherein the downhole fluid control device comprises a sliding sleeve capable of being fully opened, partially opened at varying degrees, and fully closed. 